Preliminary studies in our laboratory have demonstrated that cell mediated immune function is impaired in leukemia virus infected mice. The impairment of cell mediated immune function has been assessed by means of the macrophage migration inhibition technique and the lymphocyte mediated cytotoxicity technique. We propose to determine the kinetics of the suppression of cell mediated immune function using lymphocyte mediated cytotoxocity in mice inoculated with the Friend leukemia virus complex. Studies will be performed to determine if there is any alteration in the anti-theta susceptibility of the splenic effector cell population. The possible role of a direct leukemia virus- effector cell interaction will be evaluated. Experiments will be undertaken to determine if leukemic cells are capable of producing "factors" which have the capacity to inhibit cell mediated immune function. By the use of well defined susceptible and resistant mouse populations and the use of a well characterized virus complex (Friend leukemia virus) the above objectives are amenable to experimental analysis.